HTML::Embperl - Building dynamic Websites with Perl

Copyright (c) 1997-2001 Gerald Richter / ECOS GmbH

You may distribute under the terms of either the GNU General Public 
License or the Artistic License, as specified in the Perl README file.

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED 
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

$Id$


### !! IMPORTANT !! IMPORTANT !! IMPORTANT !! IMPORTANT !! IMPORTANT !! 
###
###
### This is the second BETA release of Embperl 2.0, before installing
### please read the README.v2. Documentation is not yet updated to
### reflect the changes in 2.0, everything that has changed is
### documented in README.v2. Since the first beta I have fixed a lot
### of smaller bugs and use it now in production environment on my own.
### But be carefull this release may still contain bugs.
###
###
### !! IMPORTANT !! IMPORTANT !! IMPORTANT !! IMPORTANT !! IMPORTANT !! 


Hints for using Embperl 2.x
---------------------------

Embperl 2 has a totaly rewritten core. It contains nearly 7500 lines 
new (mostly C-) code. Also I have done a lot of testing, there may
be still undiscovered bugs!

Please report any weired behaviour to the embperl mailing list, but
be sure to read this whole README to understand what can't work so far.

The Embperl core now works in a totaly different way. It is divided into
smaller steps:

    1 reading the source
    2 parseing 
    3 compiling 
    4 executing
    5 outputing

Further version will allow to replace every single step of this pipeline
with custom modules. Also it will be possible to cascade multiple
processors. This allows for example to have Embperl and SSI in one file
and to parse the file only once, feeding it first to the SSI processor and
afterwards to the Embperl processor. Also the parser will be exchangeable
in future version to allow for example to use an XML parser and an
XSLT stylesheet processor.

These new execution scheme is also faster, because html tags and metacommands
are parsed only once (Perl code was also (and is still) cached in 1.x)
My first benchmarks show 50%-100% faster execution under mod_perl for pages
longer then 20K (For short pages ( < 5K ouput) you won't see such a great difference)
and without any external database access.

Another new feature is that the syntax of the Embperl parser is defined
within the module HTML::Embperl::Syntax and can be modified as nessecary.
Embperl comes with a set syntax definitons which can be extened modified by
the user. So far there are syntaxdefinitions for SSI, Text only, Perl only,
ASP and a Mail taglib. You can tell Embperl which syntax to use either in
the configuration via EMBPERL_SYNTAX, or with the syntax parameter of
Execute or you change the syntax dynamicly inside the page via the
[$syntax   $] command. You also could specify more then one syntax at the same
time e.g. [$syntax Embperl SSI $] to mix Embperl tags and SSI tags in the same
page.

If you like to create your own syntax read 

perldoc HTML::Embperl::Syntax

and look at the files under Embperl/Syntax/ for examples how to do it.

Also new is the possibility to cache (parts of) the output. See
for the new configuration directives below


Debugging
---------

Starting with 2.0b2 Embperl files can debugged via the interavtive debugger.
The debugger shows the Embperl page source along with the correct linenumbers. 
You can do anything you can do inside a normal Perl programm via the debugger,
e.g. show variables, modify variables, single step, set breakpoints etc.

You can use the Perl interacive command line debugger via

    perl -d embpexec.pl file.epl  

or if you prefer a graphical debugger, try ddd (http://www.gnu.org/software/ddd/)
it's a great tool, also for debugging any other perl script:

    ddd --debugger 'perl -d embpexec.pl file.epl'


NOTE: embpexec.pl could be found in the Embperl source directory

If you want to debug your pages, while running under mod_perl, Apache::DB is the
right thing. Apache::DB is available from CPAN.


The following difference to Embperl 1.x apply:
------------------------------------------------------

- The following options can currently only set from the httpd.conf:
     optRawInput, optKeepSpaces

- The following options are currently not supported:
     optDisableHtmlScan, optDisableTableScan,
     optDisableInputScan, optDisableMetaScan

  optDisableHtmlScan can be replaced by switching the syntax e.g.

  [$syntax EmbperlBlocks $]  # same as [- $optDisableHtmlScan = 1 -]

  here goes your code, Embperl will not interpret any html tags here 

  [$syntax Embperl $]        # same as [- $optDisableHtmlScan = 0 -]


- Nesting must be properly. I.e. you cannot put a <table> tag (for an
  dynamic table) inside an if and the </table> inside another if.
  (That still works for static tables)

- optUndefToEmptyValue is always set and cannot be disabled.

- [$ foreach $x (@x) $] requires now the brackets around the
  array (like Perl)

- [+ +] blocks must now contain a valid Perl expression. Embperl 1.x
  allows you to put multiple statements into such a block. For performance
  reasons this is not possible anymore. Also the expression must _not_
  terminated with a semikolon. To let old code work, just wrap it into a do
  e.g. [+ do { my $a = $b + 5 ; $a } +]


The following things are not fully tested/working yet:
------------------------------------------------------

- [- exit -]

- safe namespaces


Embperl 1.x compatibility flag
------------------------------

If you don't have a separate computer to make the test setup, you can
include

PerlSetEnv EMBPERL_EP1COMPAT 1

at the top level of your httpd.conf, then Embperl will behave just the same
like Embperl 1.3b7. In the directories where you make your tests, you
include a

PerlSetEnv EMBPERL_EP1COMPAT 0

to enable the new engine.

but _DON'T_ use this one a production machine. While this compatibility mode
is tested and shows no problems for me, it's not so hard tested as 1.3b7
itself!


Addtional Config directives
---------------------------

Caching parameter
-----------------

execute parameter / httpd.conf environment variable / name inside page (must set inside [! !])


cache_key / EMBPERL_CACHE_KEY / $CACHE_KEY 

literal string that is appended to the cache key


cache_key_options / EMBPERL_CACHE_KEY_OPTIONS / $CACHE_KEY_OPTIONS

    ckoptCarryOver = 1,     use result from CacheKeyFunc of preivious step if any 
    ckoptPathInfo  = 2,     include the PathInfo into CacheKey 
    ckoptQueryInfo = 4,	    include the QueryInfo into CacheKey 
    ckoptDontCachePost = 8, don't cache POST requests  (not yet implemented)

    Default: all options set


expired_func / EMBPERL_EXPIRES_FUNC / &EXPIRES

function that should be called when build a cache key. The result is
appended to the cache key.


cache_key_func / EMBPERL_CACHE_KEY_FUNC / &CACHE_KEY

function that is called everytime before data is taken from the cache.
If this funtion returns true, the data from the cache isn't used anymore,
but rebuild.


Function could be either a coderef (when passed to Execute), a name of a
subroutine or a string starting with "sub " in which case it is compiled
as anoymous subroutine.


expires_in / EMBPERL_EXPIRES_IN / $EXPIRES

Time in seconds that the output schould be cached. (0 = never, -1 = forever)


Syntax switching
----------------

syntax / EMBPERL_SYNTAX / [$ syntax $]

Used to tell Embperl which syntax to use inside a page. Embperl comes with
the following syntaxes: 

    - EmbperlHTML       # all the HTML tag that Embperl recognizes by default
    - EmbperlBlocks     # all the [ ] blocks that Embperl supports
    - Embperl           # (default; contains EmbperlHtml and EmbperlBlocks)
    - ASP               # <%  %> and <%=  %>, see perldoc HTML::Embperl::Syntax::ASP
    - SSI               # Server Side Includes, see perldoc HTML::Embperl::Syntax::SSI
    - Perl              # File contains pure Perl (similar to Apache::Registry), but
                        #  can be used inside EmbperlObject
    - Text              # File contains only Text, no actions is taken on the Text
    - Mail              # Defines the <mail:send> tag, for sending mail. This is an
                        # example for a taglib, which could be a base for writing
                        # your own taglib to extent the number of available tags

You can get a description for each syntax if you type

    perldoc HTML::Embperl::Syntax::xxx

where xxx is the name of the syntax.

You can also specify multiple syntaxes e.g.

    PerlSetEnv EMBPERL_SYNTAX "Embperl SSI"

    Execute ({inputfile => '*', syntax => 'Embperl ASP'}) ;

The syntax metacommand allows to switch the syntax or to 
add or subtract syntaxes e.g.

    [$ syntax + Mail $]

will add the Mail taglib so the <mail:send> tag is available after
this line.

    [$ syntax - Mail $]

now the <mail:send> tag is unknown again

    [$ syntax SSI $]

now you can only use SSI commands inside your page.



-------------------


Enjoy

Gerald